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Advent re-foam gone bad

F

Fiddla

Member
Tried refoaming my Original Advent Masonite woofer yesterday. The glue shipped with the surrounds, a white glue, wasn't very tacky, and I struggled to attach the foam to the speaker cone. I finally got a good seal.

Attaching it to the Masonite ring was even more problematic. When I finally mounted the speaker and turned on the music, the driver did not produce a note, but a fuzzy overtone. It sounded like a blown speaker, which I suppose it was.

When I touched parts of the surround, this fuzz would go away. I have since tried regluing parts of the surround that had separated from the Masonite ring, but the speaker continues to revert to bad form.

I think I'm going to need to start from scratch. What can I use to dissolve the foam and remove it from the paper cone? This is a brand-new foam that isn't rotted, so I'm not sure how to do this.

Thanks in advance.
 
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Just took the woofer out and reinspected it. There is an area of separation where the seal did not take. It's hard getting the glue into a spot like this. The Masonite ring is not very accommodating, particularly those places around the screw mounts where the spider impedes access to the ring, I've forced some glue into the cap and am waiting for it to dry.

Let's see how this goes.
 
Did you play a tone when you glued the surround to the masonite? If not, search YouTube for refoaming videos.


Also, the white glue is water soluble. If you want to start over, I would do it before the glue sets up. Dab water at the surround to masonite seal until the surround separates. Wipe off all the old glue and give it time to dry up before restarting.

Also, when using the white glue, you need to either clamp the joint or keep pressing the surround in place. That glue has a long working time, that is, it takes a long time for it to set up. It can take 10 to 20 minutes for the glue to set up enough where you can stop pressing it in place.
 
I think I might be barking up the wrong tree.

I observed the speaker while it was misbehaving. When I put my finger on some parts of the surround/cone seal, it buzzes more loudly. On other parts of the arc, the buzz goes away.

I pulled the buzzing woofer out yet again. I noticed when I pushed up on the speaker cone, I heard a rubbing sound. This didn't happen when I depressed the cone, only when I lifted it toward me.

I think that is the path of the cone in any case, right, in the direction toward the listener?

I think I've got to rip this foam out and start again.

*sigh*
 
My first re-foam had to be repeated and that was several days after completing the job. What work I did, I did correctly but the guy at the store where I bought the foams, sold me some intended for car subs. As was said to me later, I turned my woofers into midranges.

By then the glue had cured so it was rediculously time consuming use of a razor blade and particular scraping knife to get the unwanted foam and hardened adhesive off of two 12" woofer cones and baskets.
 
Fiddla said:
I think I might be barking up the wrong tree.

I observed the speaker while it was misbehaving. When I put my finger on some parts of the surround/cone seal, it buzzes more loudly. On other parts of the arc, the buzz goes away.

I pulled the buzzing woofer out yet again. I noticed when I pushed up on the speaker cone, I heard a rubbing sound. This didn't happen when I depressed the cone, only when I lifted it toward me.

I think that is the path of the cone in any case, right, in the direction toward the listener?

I think I've got to rip this foam out and start again.

*sigh*
Click to expand...

A driver should not make any rubbing noises when the cone is evenly pushed down or lifted up. Depending upon the gap the voice coil fits into, pushing only on one side or the other of the cone can cause rubbing.

When you foamed the woofers, how did you center the VC? Using a 30 to 40 Hz cone will magnetically center the VC in the gap. Advents are known for having a wide gap and many experienced people can successfully refoam them by manually centering the VC.
 
I followed this video, which seemed pretty methodical and fool-proof:

But they don't spend a lot of time on the centering of the cone on the spider. They pretty much suggest that once you have the foam attached to the cone, the outer rim will seat itself.

Also, he's using a different kind of glue than I was using, which seemed to tack up a lot more quickly.

There are obviously different glues for the job. I didn't think the white glue was tacky enough (probably it wasn't tacky quickly enough), so I switched to Duco Cement halfway through the job. Probably not the best move, but I was able to remove it without too much trouble.

In removing the foam from the Masonite and the cone (using acetone and H2O, depending on which glue I had used), I noticed the surround wasn't absolutely symmetrical, that is, some of foam on the Masonite ring was set further back from the edge than some other parts. I guess that should have been the tell right there.

The tricky thing is, you got just a few minutes to situate the cone before the glue sets up.

In other words, a harder job for the newbie than I was led to believe.

I am going to investigate other centering methods, including the iPhone method. But I'm not sure it works on this Masonite woofer, because the outer rim of the foam does not rest upon the spider, but rather must be glued UPWARD to mate with it.

Henry Kloss, you rascal, you! Nonetheless, we salute you.
 
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Fiddla said:
I followed this video, which seemed pretty methodical and fool-proof:

But they don't spend a lot of time on the centering of the cone on the spider. They pretty much suggest that once you have the foam attached to the cone, the outer rim will seat itself.

Also, he's using a different kind of glue than I was using, which seemed to tack up a lot more quickly.

There are obviously different glues for the job. I didn't think the white glue was tacky enough (probably it wasn't tacky quickly enough), so I switched to Duco Cement halfway through the job. Probably not the best move, but I was able to remove it without too much trouble.

In removing the foam from the Masonite and the cone (using acetone and H2O, depending on which glue I had used), I noticed the surround wasn't absolutely symmetrical, that is, some of foam on the Masonite ring was set further back from the edge than some other parts. I guess that should have been the tell right there.

The tricky thing is, you got just a few minutes to situate the cone before the glue sets up.

In other words, a harder job for the newbie than I was led to believe.

I am going to investigate other centering methods, including the iPhone method. But I'm sure it works on this Masonite woofer, because the outer rim of the foam does not rest upon the spider, but rather must be glued UPWARD to mate with it.

Henry Kloss, you rascal, you! Nonetheless, we salute you.
Click to expand...

For experienced refoamers, the video you posted is fine. I've done it that way, but only after I gained enough experience working with other methods. Applying a tone is easy and foolproof, provided you don't go crazy and raise the volume too high. At 30to 40 Hz you will see the cone move in and out. A little visible movement is fine. The tone will magnetically center the cone, allowing you to ensure the surround is properly centered.

When I refoamed my OLA, I applied glue and attached the surround to the masonite. It has been a few months and I don't remember if I used Aleen's Tacky Glue or the clear, solvent glue. I think it was Aleen's because that is all I use now.

I turned on the tone after I seated the surround against the masonite. Once I was satisfied, I turned off the tone and kept pressing the surround against the back of the masonite ring. After a few minutes, I turned on the tone to confirm that all was good. I also alternatingly pressed on and lifted the cone in different places to get a feel for the centering of the cone.
 
Fiddla said:
Thanks, RTally, I think I will try this out.
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If you use slow-setting glue, like the white glue, you have time to play with it. That is fine when you are learning because you have time to experiment before the glue sets. I suggest playing with the cone before the glue sets. For example, if the air gap is small enough (not really the case with Advents), you can press down on one side of the cone and hear it rub. If the VC is centered, pressing down on the opposite side should also make it rub the same way. If it rubs on one side, but not the other, then the VC is not centered.

If the surround separates from the masonite ring, just press it back in place. I always test with a tone before calling it done.
 
Another option is to use a solvent-based glue which has lower work time, better adhesion, better grab, some degree of removeability, and greater flexibility. Generally neoprene or some other rubber dissolved in a combination of toluene and xylene, with the mix determining work time.

Solvent glues were originally used. Ken Kantor has extensively posted on AK about the importance of glue selection, and why replacing surrounds or cones generally alters the sound.

Such glues have fallen into disfavor because the solvents can be hepatotoxic, nephrotoxic, neurotoxic, and lead to listening to the Ramones. That can be true with daily exposure, but the minor exposure for a surround replacement, particularly when performed in a well-ventilated area, is not likely to be problematic.
 
OLAs were my first attempt to refoam,,, Some of the success is due the help and info I got on this forum,,, and taking the advice of getting Rick Cobbs kit,, proper foam, glue, tone CD and detailed instructions... They sound great from the first try 5 years ago, and still do...
 
drumbum said:
Shimming is the only way to fly.
Click to expand...

I respectfully disagree my friend. Shimming WAS the only way for me, before I started using the tone generator method. Shimming can cause major issues by cutting into the dust caps, shoving shims down the air gaps and damaging the coil wires, accidentally cutting the tinsel leads while cutting the dust cap etc etc. I know, I've been there and done that. I use the much safer tone generation now and have successfully repaired many vintage speakers that way.

A couple of tips for the OP -

1) Make sure the basket edge and cone lip are as clear of old glue residue as you can possibly get them. Personally, I run a fine grit of sandpaper VERY carefully around the basket mating surface and the cone lip.
2) Make sure you refoam on the correct side of the driver cone. Some surrounds are applied to the back edge of the cone,some to the front edge. Getting this wrong WILL cause problems because the cone will ride too high or low in the motor.
3) Use a turntable (like a potter's wheel or something) if you can. It's really helpful to spin the speaker round while working on it.
4) If applying the surround to the front side of the cone (the most common type) then use something inserted into the metal basket frame, beneath the cone, to lift the cone up off the basket edge. I use a few balls of squashed up tissue paper. This raises up the surround edge away from the basket edge, so you can apply your glue in a clean bead without the surround lip constantly getting in the way.
5) Use a tone. Any smartphone will have an app available to generate a 50hz tone. Apply your glue to the basket edge, in a thin even bead, remove your supporting tissues or what ever, start the tone, then drop the surround onto the glue bead.
6) Don't go around the surround in a circular fashion, pushing it onto the glue. Use a 12, 6,3,9 type approach, a bit like torquing down a cylinder head if you're mechanically minded.
7) If you hear a buzzing, this is the coil rubbing inside the motor. Gently press around the surround until the buzzing stops. Wait for a while and if no more buzz, leave the glue to set and stop the tone.
8) Don't worry about the surround edge buckling up or wrinkling - this will tighten up as the glue dries.
9) Don't rush, take your time and keep your fingers / workspace clean.

If you find you have a buzz when the woofer is installed in the cabinet, check for lose touching wires. This could also be caused by 'spider sag' - a good way to fix this is to rotate the woofer though 180 degress so that it is installed the opposite way to what it was originally.

Hope this helps and good luck :-)
 
That's a good article on shimming, @grillebilly

I will say one thing - using shims does allow you to set the cone height and ensure the spider is level.

You can see from the images in the article though, just how close to the cut line of the dust cap those tinsel leads are. Yikes !
 
Check that the spider hasn't partially separated from the coil former. Had that problem on the last Masonite Advent woofer I refoamed.
 
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colohiker said:
Check that the spider hasn't partially separated from the coil former. Had that problem on the last Masonite Advent woofer I refoamed.
Click to expand...
same here , also had one with the spider completely separated from the former , 5 min. epoxy and shimming was the fix.
 
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I downloaded a really nice tone generator app today and am waiting for the new surround to arrive from Mr. Cobb. I predict success this time.

Also picked up a bottle of Aleene's Quick Dry Tacky Glue.

Loaded for bear.

Will let you know how it turned out.

Thanks for all the great advice!
 
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